Method of manufacturing spherical and cylindrical bearings

ABSTRACT

A bearing assembly having bearing surfaces pre-loaded towards each other, the bearing surfaces being originally made in slightly non-conforming geometry and dimensions over the majority of their surface areas in sliding engagement, the areas of the bearing surfaces in engagement being thus less than the total available areas. During use, and through progressive wear-in of the bearing surfaces in engagement, the bearing surface areas in engagement are progressively enlarged with progressive conformity in geometry and dimension, the conforming surface areas being constantly kept in engagement by the elements in the assembly adapted to provide bearing pre-load.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 356,368, filedMar. 9, 1982, for SPHERICAL AND CYLINDRICAL BEARINGS AND METHOD OFMANUFACTURING, now U.S. Pat. No. 4,493,512, issued Jan. 15, 1985 whichis a continuation in part of application Ser. No. 286,470, filed July24, 1981, for INTEGRALLY SEALED VIBRATION BALL AND SOCKET JOINTS, nowU.S. Pat. No. 4,386,869, all assigned to the same assignee as thepresent application.

BACKGROUND OF THE INVENTION

The present invention relates to bearings in general, and moreparticularly to spherical and cylindrical bearings wherein the engagedbearing surfaces of an inner member and of an outer member arepre-loaded toward each other. The present invention contemplates thatthe bearing surfaces in engagement be provided with a particulargeometry different at the time of manufacturing from the geometry whichis finally obtained after a wear-in period.

The invention has particular applications to spherical bearings of theball and socket type as are of general use in motor vehicle steeringtie-rod assemblies, for example, and to both cylindrical and sphericalbearings which are of general use in drag links, torque rods, suspensionstabilizers, shock absorbers and friction snubbers, for example, inpassenger cars, trucks, trailers, military vehicles, railroad vehicles,and the like.

It is customary to manufacture ball and socket bearings and cylindricalbearings for such use under exacting machining and assemblyrequirements, in order to provide heavy load bearing capability and longlife under adverse conditions. For example, bearing surfaces inswivelling or rotary engagement are usually machined to the geometricshapes and to dimensions as accurate as technically feasible, withnarrow tolerances and with exacting surface finishes. Such methods ofmanufacturing are not compatible with mass production at a reasonablylow cost per unit, and the tolerances required may lead to bearinglock-up during assembly or after installation on a vehicle.

SUMMARY OF THE INVENTION

The present invention provides spherical and cylindrical bearingswherein the bearing surfaces in engagement are, by design, not strictlyconforming with each other, but which, during usage, progressively wearinto conforming bearing surfaces, the bearing pre-load and wearcompensation means, forming part of the bearing assembly, taking up theplay between the bearing surfaces that would normally occur during thewear-in period and during normal use subsequent to the wear-in period.The present invention accomplishes its objects by providing conformityof geometry and sizes, within usual manufacturing tolerances, only withrespect to relatively small areas of the bearing surfaces in swivellingor rotational engagement, until the areas in bearing engagement havegradually worn to a specific target geometry resulting in full area ofengagement between the bearing surfaces.

These and many other objects and advantages of the present inventionwill become apparent to those skilled in the art when the followingdescription of the best modes contemplated for practicing the inventionis read in conjunction with the accompanying drawing, wherein likereference numerals refer to like or equivalent parts, and in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial longitudinal sectional view of an example ofspherical bearing of the stud-ball and socket type according to thepresent invention;

FIG. 2 is a cross-sectional view thereof along line 2--2 of FIG. 1;

FIG. 3 is a partial view similar to FIG. 1, but at a much enlarged scalefor showing the non-conforming geometry of the bearing surfaces inengagement after assembly of the joint;

FIG. 4 is a view similar to FIG. 3 but showing the relative position ofthe diverse elements after wear-in of the bearing surfaces;

FIG. 5 is a partially longitudinal sectional view of an example ofcylindrical bearing according to the present invention shown in thecondition existing after assembly of the diverse elements;

FIG. 6 is a view from line 6--6 of FIG. 5;

FIG. 7 is a view similar to FIG. 5, but showing the relative position ofthe diverse elements after initial wear-in of the bearing surfaces; and

FIG. 8 is a view from line 8--8 of FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawing, and more particularly to FIGS. 1-3 thereof, anexample of structure for a knuckle or swivel joint 10 according to thepresent invention is, for example, of the type as disclosed in detailsin co-pending application Ser. No. 286,470, now U.S. Pat. No. 4,386,869.The knuckle or swivel joint 10 comprises a stud 12 provided at one endwith an integral cold-headed ball 14 having a peripheral convexspherical surface 16, provided with an equatorial annular lubricationgroove 18 and a flat end face 19. The stud 12 has a cylindrical endportion, not shown, provided with a peripheral thread and a taperedportion 22 for engagement in the correspondingly tapered bore of a firstjoint member, not shown, such as a steering arm or rod, a stabilizer armof the like, a nut, not shown, threading over the threaded end of thestud 12 for fastening the stud 12 to the first jointed member, as iswell known in the art. In the example of structure illustrated, thetapered portion 22 of the stud 12 is integrally connected to the ball 14by a portion having a reverse taper, as shown at 24, along a circularline 26.

The spherical member or ball 14 is disposed in a cylindrical housing orshell 28 normally clamped or otherwise fastened to a second joinedmember, not shown. The shell 28 has a tubular body portion 30, made ofsteel or similar material, provided with a transverse radial flange 32at one end and another transverse radial flange 34 at the other end, thetransverse flanges 32 and 34 each forming an opening, 35 and 36,respectively. The shell 28 has an internal bore 38 adapted to freelyreceive a bearing ring 40. The bearing ring 40, made of steel, bronze,or, as illustrated, high strength plastic, has a generally sphericalconvex inner surface 42 in swivelling engagement with the sphericalsurface 16 of the ball 14, provided with a pair of parallel annulargrooves 44. The bearing ring 40 has large diameter symmetricallydisposed peripherally cylindrical ends 46 and a cylindrical peripheralsurface 48, a pair of frusto-conical or inclined surfaces 50 joining thecylindrical peripheral surface 48 to the cylindrical ends 46 of thering. The bearing ring 40 is preferably made of two separate sections40a and 40b, FIG. 2, such that, when placed over the ball 14, the twohalf rings 40a and 40b are separated by an average clearance gap 52. Thebearing ring may also be made of three, four or more portions. With thebearing ring 40 disposed around the ball 14, the overall outer diameterof the cylindrical peripheral surface 48 of the bearing ring 40 isslightly less than the diameter of the inner bore 38 of the shell 28,with the result that an annular clearance, shown somewhat exaggerated at54, exists all around the bearing ring 40 between its peripheral surface48 and the surface of the internal bore 38 of the shell 28. Theclearance 54 is normally very narrow and practically non-existent afterthe elements constituting the knuckle and swivel joint 10 are assembled.

A combination compression and seal ring 56 is disposed within the bore38 of the shell 28 on one side of the bearing ring 40. The combinationcompression and seal ring 56 has a tapered end face 58 conforming to theshape of the tapered or inclined peripheral surface 50 of the bearingring 40, and a peripheral cylindrical surface 60 disposed within thebore 38 of the shell 28. The combination compression and seal ring 56has a radial annular surface 62 disposed in engagement with the innersurface of the shell and flange 34, and a cylindrical inner annularsurface 63 engaged with the peripheral cylindrical end surface 46 of thebearing ring 40. A bellows seal or boot 64 is, preferably, integrallymolded with the compression and seal ring 56. The bellows seal or boot64 has a relatively thin wall flexible tubular body portion 66terminating in an elastic annular integral garter flange 68. Thecombination compression and seal ring 56 is made of any appropriateelastomeric material such as natural rubber, synthetic rubber,polyurethane, or the like, and the garter flange 68 at the end of thebellows seal body portion 66 forms the edge of an opening 70 of a muchsmaller diameter than the largest diameter portion of the stud 12 at thejunction line 26 between its tapered surface portion 22 thereof and itsreverse taper portion 24. Preferably, the surface of the garter flange68 has a slightly V-shaped surface 70, as seen from a section throughthe edge, such as to elastically conform with the shape of the studperiphery at the junction of the two tapered surfaces 22 and 24 alongthe junction line 26 and to remain firmly in position, as shown in FIG.1.

The tapered end face 58 of the combination compression and seal ring 56may be provided with a plurality of longitudinal grooves, not shown,which enable the compression ring portion 63 to be subjected toconsiderable compression stress and to absorb shocks and vibration.

A compression ring 74 is disposed on the other side of the bearing ring40, symmetrically to the combination compression and seal ring 56. Thecompression ring 74, made of the same material as the combinationcompression and seal ring 56 and also preferably provided withlongitudinal stress relieving grooves, has a tapered end face 76 engagedwith the other tapered or inclined peripheral surface 50 of the bearingring 40, a peripheral cylindrical surface 78, an end annular face 80,and an inner cylindrical surface 81. The compression ring 74 is disposedcompressed within the bore 38 of the shell 28, its end annular face 80engaging the surface of the transverse flange 82 formed at the edge of aretainer and closure cap 84 which is in the form of a dome-shaped body87.

The diverse parts forming the ball and socket joint 10 are assembledfrom one end of the shell 28, prior to forming one of the end radialflanges 32 or 34, with the space 89 between the ball 14 and the interiorof the pleated body portion 66 of the bellows seal 64 packed with anappropriate high temperature water-resistant lubricant such as grease,the space 91 between the dome-shaped body portion 87 of the retainerclosure cap 84 and the flat end face 19 of the ball 18 being also filledwith an appropriate lubricant such as grease. After the diverse partsare placed in the shell 28, one of the end flanges 32 or 34 of the shell28 is bent over by swaging the corresponding rim of the shell 28, suchas to form the annular retaining end flange. The annular retaining endflange, 32 or 34, is formed such as to exert a certain amount ofpressure directed parallel to the longitudinal axis of the assemblywhich applies firmly the flange 82 of the retainer closure cap 84against the annular surface 80 of the compression ring 74, and such asto exert considerable pressure on the corresponding tapered surface 50and cylindrical surface 46 of the bearing ring 40 via the taperedsurface 76 and the inner cylindrical surface 81 of the compression ring74, now placed under compression. Simultaneously, the combinationcompression and seal ring 56 is compressed between the inclined end face50 of the bearing ring 40 in engagement with the tapered surface 58 ofthe compression and seal ring 56 and the end flange 34 of the shell 28.The forces exerted by the compression ring 74 and the combinationcompression and seal ring 56 are applied to the opposite inclinedsurfaces 50 and to the surface of the cylindrical ends 63 of the splitbearing ring 40, with the result that a considerable radial force isexerted on the split bearing ring 40 which causes the bearing surface 42of the bearing ring to firmly engage the peripheral spherical surface 16of the ball 14 at their areas in mutual contact.

Conventional bearing manufacturing methods require that the sphericalsurface 16 of the ball 14 be machined and ground to a substantiallyexact dimension and to a substantially precise spherical shape, and thatthe convex spherical surface 42 of the bearing ring 40 be machined andground to substantially the same dimension as the spherical surface 16of the ball 14, and be as spherical as possible such as to provide largeareas of engaging surfaces in conforming dimensions and shape. Largebearing areas are required to permit effective transmission of loadsbetween bearing surfaces without substantial permanent deformations ofthe surfaces, without sizing, and without embrittlement of the surfacelayers. The present invention, by contrast, contemplates that only smallareas of the ball surface 16 and of the bearing ring surface 42 be atfirst in engagement with each other when the bearing unit ismanufactured, and that the areas of the bearing surfaces in engagementprogressively increase during wear-in of the unit, such wear-in beingeffected either after installation of the unit on a vehicle, or as aresult of operating the ball and socket joint for an appropriate periodof time under artificial load in a wear-in fixture providing motion ofthe ball 16 in all directions relative to the bearing ring 40. Theinvention provides that the ball 14 be ground with an appropriatespherical surface 16, and that the convex spherical surface 42 of thebearing ring 40 be finished, for example by grinding, according todifferent spherical surfaces of slightly different radii.

For example, as illustrated in detail, and in an exaggerated manner, atFIG. 3, the bearing ring surface 42 is generated according to aspherical surface substantially conforming to the spherical surface 16of the ball 14 over narrow widths defined between the envelope of pointsA and the envelope of of points B between one of the lubrication grooves44 and the edge of the bearing ring, and between the envelope of pointsC and the envelope of points D between the other lubricating groove 44and the other edge of the bearing ring 40. Each of the spherical sectorsdefined between the points A and the points B envelopes and between thepoints C and the points D envelopes may be machined in a range as narrowor as wide as desired, thus resulting in an almost single circular linecontact at one extreme of the range, or in more or less wide sphericalsector area contacts between the ring bearing surface 42 and theperipheral spherical surface 16 of the ball 14 at the other extreme ofthe range and as shown respectively at 86 and 88 at FIG. 3. The portionof the ring bearing surface 42 between the lubrication grooves 44 ismachined as a spherical surface of slightly larger radius, as shown at90, and the portions between the circular line formed by the envelope ofthe points B and the first lubrication groove 44, shown at 92, increaseprogressively in radius to a dimension at most that of the radius of thespherical surface 90. In the same manner, the area 94 between theenvelope of the points C and the edge of the other groove 44 increasesin radius to a dimension at most that of the radius of the sphericalsurface 90. Similarly also, the surface area comprised between theenvelope of the points A and the edge 96 of the bearing ring surface 42is relieved, as shown at 98, and also relieved, as shown at 102, is thearea portion between the envelope of the points D and the other edge 100of the ring bearing surface 42. In view of the relieved surface portions98 and 102, the bearing ring edges 96 and 100 are prevented from digginginto the spherical surface 16 of the ball 14.

For example, the spherical zone 90, between the lubrication grooves 44,may be formed concentric to the ball 14 with a radius a few micronslonger than the radius of the ball spherical surface 16, and thespherical zones 86 and 88 formed with the center of the spherical zone86 being on one side and the center of the spherical zone 88 being onthe other side of the axis of symmetry of the nominal spherical surface42 of the bearing ring 40, the radii being substantially equal to thatof the spherical zone 90. Alternatively, the surfaces of the spericalzones 86, 90 and 88 may be formed from a common center, the radius ofthe spherical zone surface 90 being slightly longer than the radii ofthe spherical zones 96 and 98, respectively.

In the structure illustrated, the ball 14 is preferably made of amaterial which is more resistant to wear than the material, plastic forexample, of which the bearing ring 40 is made such that, through normalwear during the wear-in period of the bearing unit, the spherical zonesurface areas 86 and 88 progressively wear in such a manner thateventually the total area of the ring bearing surface 42 is inengagement, as shown at FIG. 4, with the spherical surface 16 of theball 14. The split bearing ring 40 is constantly urged by the pre-loadforce exerted by the elastomeric compression ring 74 and the combinationcompression and sealing elastomeric ring 56 such as to compensate forwear during a predetermined wear-in period, and for normal wear of thebearing surfaces in service, with a corresponding progressive narrowingof the gaps 52, FIG. 2, between the ring portions 40a and 40b, and withprogressive widening of the clearance 54, FIGS. 1 and 4, between thesurface of the bore 38 in the shell 28 and the peripheral surface 48 ofthe bearing ring 40.

It will be readily apparent to those skilled in the art that byproviding a pair of narrow spaced apart spherical zone bearing surfaces86 and 88, FIG. 3, in engagement with the spherical peripheral surface16 of the ball 14, the ball 14 and its socket defined by the bearingring 40 are maintained constantly substantially concentric, even whensubjected to forces directed along the axis of the stud 12, FIG. 1,which would not be the case of the bearing surface 42 of the bearingring 40 were conformed to the same dimensions and the same shape as thespherical surface 16 of the ball 14, as is conventional in the art. Inconventional structures, the longitudinal forces tend to open up thecurvature of the bearing surface 42, with the result that the areas ofthe ring bearing surface 42 in engagement with the spherical peripheralsurface 16 of the ball 14 tend to be limited only to a narrow areabetween the grooves 44. Through progressive wearing-in and widening ofthe spherical zone areas 86 and 88, in structures according to theinvention, and under the wear take-up action of the elastomericcompression rings 74 and 56, the shapes of the bearing ring convexspherical surface 42 and of the peripheral spherical surface 16 of theball 14 progressively conform with each other, irrespective of any smallimperfection that may have existed when the bearing unit was firstinstalled and placed in service.

The same principles are applicable to bearing units other than sphericalbearings, such as, for example, the cylindrical bearing unit 110 ofFIGS. 5-8. The cylindrical bearing unit 110 is typical of drag-linkinter-member connection or suspension system attachment joints wherein amember, not shown, is attached to an inner member defined by acylindrical rod 112 which, in some applications, may be tubular, at theportions of the rod 112 projecting on each end of a housing or shell 114which, in turn, is clamped in or otherwise fastened to another member ofthe drag-link or suspension assembly, not shown. A split bearing ring orsleeve 116 is disposed in the shell 114, coaxially with the rod 112, andis constantly urged with its substantially cylindrical bearing surface118 in engagement with the cylindrical peripheral surface 120 of theinner member or rod 112 by a pair of compressed elastomeric rings 122compressibly fitted between the bore 124 of the shell 110 and a reduceddiameter portion 126 formed at each end of the bearing ring or sleeve116. The split bearing ring or sleeve 116 has a peripheral cylindricalsurface 128 fitting within the bore 124 of the shell 114, and is heldwithin the shell 114 by radially formed end flanges 130, such that thecompression elastomeric rings 122, in addition of being compressedradially between the shell bore 124 and the reduced diameter endcylindrical surfaces 126, are compressed laterally between the innersurface or the end flanges 130 and the annular step surface 132 formedat the junction between the sleeve cylindrical peripheral surface 128and the reduced diameter end surfaces 126. As best shown at FIG. 6, thesplit bearing ring or sleeve 116 is split preferably along its diametersuch as to form two half-sleeve portions 116a and 116b separated byspaces or diametrically disposed gaps 134, such that the sleeve bearingsurface 118 is urged constantly in engagement with the peripheralsurface 120 of the inner member or rod 112 under the pre-load forceprovided by the compressed elastomeric rings 122.

According to the present invention, the bearing surface 118 of the splitbearing ring or sleeve 116 is purposely made non-cylindrical, such as toengage the peripheral surface 120 of the inner member 112 only alongrelatively narrow bands, symmetrically disposed as shown at 136, anarcuate surface, as seen in profile and as shown at 138 in a somewhatexaggerated manner at FIG. 5, being disposed between the contactsurfaces 136. A relief non-contact area is provided beyond each of thecontact areas 136, as shown at 140. During wear-in of the bearing unit114, in the course of which the inner member 112 is constantlyoscillated in rotation relative to the split bearing ring or sleeve 116,the contact band areas 136 progressively widen until the bearing surface118 of the split ring or sleeve 116 engages the full area of theperipheral surface 120 of the inner member 112 from one end to the otherof the split bearing ring or sleeve 116, as shown at FIG. 7, such thatfull load forces can be transmitted from the inner member 112 to thesplit bearing ring or sleeve 116. During the progressive wearing of thesurfaces, under the pre-load radially directed force exerted by theelastomeric compression rings 122, the compression rings progressivelyexpand and the clearance gap 142 between the larger diameter peripheralsurface 128 of the split bearing ring or sleeve 116 and the inner bore124 of the shell 110 is progressively enlarged, with progressivereduction in width of the gaps 134 between the bearing ring or sleeveportions 116a and 116b. In most installations, because the inner member112 is subjected to little, if any, longitudinal displacement relativeto the bearing ring or sleeve 116, it does not matter if the surfacewear is evenly distributed between the peripheral surface 120 of theinner member 112 and the bearing surface 118 of the bearing ring orsleeve, as the overall result is eventual exact conformity between thegeometry of the peripheral surface 120 of the inner member 112 and thegeometry of the bearing surface 118 of the bearing ring or sleeve 116.

Although the invention has been described and illustrated relative tobearing assemblies comprising an inner member of finite shapeconfiguration and an outer member in the form of a split ring havingonly limited areas of finite complementary shape configuration adaptedto wear-in to full areas of complementary shape configuration, it willbe apparent to those skilled in the art that the inner member may beformed such as to present limited areas of its bearing surface of finiteshape configuration adapted to wear-in to full area shape configurationcomplementary to that of the bearing surface of the outer member, andthat areas of finite shape configurations may be distributed on thebearing surfaces of both the inner and the outer members.

Having thus described the present invention by way of structuralexamples of spherical and cylindrical bearings made in accordance withthe present invention, modifications whereof will be apparent to thoseskilled in the art.

What is claimed as new is as follows:
 1. A method of manufacturing abearing comprising an inner member having a peripheral surface ofregular predetermined contour, a hollow shell, a bearing ring disposedin said shell and having a bearing surface in sliding engagement with aperipheral bearing surface of said inner member, and means between theinner surface of said shell and the peripheral surface of said bearingring for biasing the bearing surface of said bearing ring towards theperipheral bearing surface of said inner member, said method comprisingforming said bearing surfaces such that major areas of the bearingsurfaces are non-conforming in shape to a slight degree and the bearingsurfaces in sliding engagement have each a minor area substantially lessthan the total bearing surface area available, inserting said bearingring into said hollow shell and onto said inner member with said biasingmeans disposed between the inner surface of said shell and theperipheral surface of said ring to preload and cause engagement of saidminor area of said ring with said inner member, and wearing-in saidsurfaces in sliding engagement for progressively causing an increase inareas of said surfaces in sliding engagement, wherein the bearingsurface of said bearing ring and the peripheral bearing surface of saidinner member in sliding engagement mutually engage after assembly atportions intermediate the ends of said bearing ring available bearingsurface.
 2. The method of claim 1 wherein said surfaces are sphericalsurfaces.
 3. The method of claim 1 wherein said surfaces are cylindricalsurfaces.